1. Field of the Invention
This invention relates, generally, to diagnostic tests having utility in connection with the study of growth hormone disorders. More particularly, it relates to the use of somatostatin as a diagnostic test where the degree of growth hormone suppression is observed.
2. Description of the Prior Art
Human growth is believed to be regulated, at least in part, by a hormone secreted by the pituitary gland; the hormone has been identified and is known as the growth hormone. The normal endogenous secretion of growth hormone is dependent upon the interplay of growth hormone releasing factor and somatostatin. The components of this system are the hypothalamic-pituitary axis and the higher brain centers of the central nervous system.
Accordingly, dysfunction of the pituitary gland, at least in relation to its secretion of the growth hormone, may be responsible for dwarfism and gigantism as well.
There are known methods whereby growth hormone secretion by the pituitary gland can be provoked. Prior to the present invention, diagnosis of a child of unusually short stature included provoking said secretion, observing the results and little more.
This prior art procedure of employing provocation as a diagnostic tool, while having utility, requires improvement. There are many types of growth hormone disorders, and there is a need for a more powerful diagnostic tool to aid the physician. The provocative test itself, standing alone, does not suggest any further procedures that could substantially enhance the specificity of the diagnosis.
Moreover, the definition of growth hormone deficiency based on provocative testing of growth hormone secretion may not accurately reflect the total endogenous output of growth hormone secretion.
For example, where less than 10 ng/mL (nanograms per milliliter) of the growth hormone is secreted after two or more provocative tests, a diagnosis of classical growth hormone deficiency may be in order, in accordance with prior art teachings. Where greater than 10 ng/mL of growth hormone are secreted after two or more provocative tests but where the concentration during a 24 hour study is low (blood sampling every 20 minutes), a diagnosis of growth hormone neurosecretory dysfunction may be in order. Other responses can lead to a diagnosis of hypersomatotropism.
The hormone somatostatin (sold under the trademark Stilamin and manufactured by Serono Laboratories, Inc.) and its analogs or chemical equivalents, is known to inhibit the secretion of growth hormone. Theoretically, it could be used in the treatment of gigantism. Heretofore, no known diagnostic procedure relating to growth dysfunction had employed somatotatin as a diagnostic tool.